Railroad track rails are subject to wear by the passage of trains over the rails. In particular, depressions in the upper surface of a rail may develop such that the rail head presents an undulating, corrugated surface. Moreover, the rail may develop burrs, or otherwise lose its symmetrical profile. Maintenance of smooth running surfaces on railroad track rails is important for reasons of safety, riding comfort, protection of the track, track bed and rolling stock, noise suppression, and reduced maintenance of the track and track bed.
Grinding machines for maintaining railroad track rails in smooth, properly shaped condition are known. Such grinding machines generally comprises a plurality of rotatable grinding modules carried by a locomotive or the like in close proximity to the rail head surfaces of a railroad track. The grinding modules include rotatable, abrasive grinding stones that can be lowered into a position flush with the rail surface to grind and restore the rail surface to a smooth, desired profile.
The grinding modules of such grinding machines includes replaceable, abrasive grinding stones that are rotated about a grinding axis. The condition of the grinding stones directly affects the quality of grinding. More particularly, the grinding stones preferably present a generally flat, annular grinding surface, that is perpendicular to the axis of rotation of the grinding stones. While the grinding surface of a grinding stone is of course altered and worn in the grinding process, the grinding surface can be maintained essentially flat and perpendicular to the grinding axis by grinding only on the inner diameter of the stone. That is to say, placement of the annular grinding surface on the rail should be such that the rail sides do not extend beyond the inner diameter of the grinding stone. Moreover, it has long been considered preferable to have the grinding marks left by the grinding stone on the railhead be perpendicular to the rail longitudinal axis. Such perpendicular grinding marks are left when the grinding is done on the inner diameter of the stone. More precisely, perpendicular grinding marks are left on the railhead when the line of contact between the grinding stone and the railhead is along a diameteral line of the grinding stone, perpendicular to and intersecting the grinding axis of rotation.
Grinding modules, with their attached grinding stones, can be tilted to accommodate grinding of railheads in planes other than the horizontal. Tilting of the grinding stone about a tilt axis oriented above and along the rail, however, shifts the line of contact of the grinding stone with the rail away from the diameteral line of the stone, and, depending on the angle, can shift the grinding contact away from the inner diameter of the stone. In short, tilting of the grinding stone, although necessary in order to shape the profile of a rail, can cause uneven wear of the stone and can leave grinding marks transverse to the perpendicular of the rail longitudinal axis.
Another consideration when grinding rails to a desired profile is the presence of obstructions to the grinding stone. At road crossings, where the track intersects a highway for instance, wooden ties or rubber guards are typically brought into close proximity of the track rails to allow for smooth passage of wheeled vehicles across the track rails. Tilting of the grinding modules and grinding stones to shape the profile of the railhead can bring the grinding stones into interfering contact with the wooden ties or rubber guards.
Finally, the grinding modules of rail grinding machines are typically raised into storage positions on the supporting locomotive or the like when not being operated to grind rails. The modules must therefore be lowered and propery oriented along the rail head prior to conducting grinding operations. The rail contacting support mechanisms for initially positioning and orienting the grinding modules are typically larger and more expensive than the size of wheels or other rail contacting support mechanisms required to maintain the modules in proper orientation once in place. In the past, the functions of orienting the grinding modules and supporting the grinding modules once in place have been combined into a single support device. While only a small area of the support device is subjected to continuous contact with the railhead, the entire device must be discarded when the device becomes worn.